Today's enterprise data centers store ever-larger amounts of business critical data that must be immediately and continuously available, and highly reliable. Any down time for a storage system is considered unacceptable. Many precautions are taken in storage systems to protect against the effects of failures so that down time is avoided. However, from time to time a storage system, such as a storage array, must be upgraded or replaced.
In order to replace a current storage array with a new storage array, all the data and connections on the current storage array must be migrated to the new array. Then the storage system requires re-initialization, and host systems must be reconfigured. This requires at least some down time to complete; thus, host applications lose access to the storage array for some amount of time. Interruption of critical applications is unacceptable.
What is needed is a way to upgrade or replace storage arrays in a manner that is transparent to the host systems so that host applications are not interrupted by the upgrade or replacement.